The present invention relates to an electrical switchgear having a common housing for a thermostatic expansion material element and at least two electrical snap switches that can be actuated by a working piston of the expansion material element. The snap switches contain a switching tongue that can be swivelled between two switching positions and to which a switching spring is applied, the other end of the spring being coupled to a switching rocker that is swivelled by the working piston and is disposed on a holding plate.
An example of switchgear of the above-described type is shown in U.S. Pat. No. 4,374,373 having two snap switches that are equipped with their own switching tongues and their own switching springs. The switching tongues of the snap switches are supported at a joint holding plate on which a switching rocker is also disposed. Both snap switches have this switching rocker in common, the two switching springs being coupled to the switching rocker. This known switchgear allows two independent switching operations that can be carried out at different temperature stages. The advantage of the known construction is that only a low overall size is required and that for both snap switches, several components can be used jointly, particularly the switching rocker and the corresponding holding plate.
An objective of the present invention is to provide an electrical switchgear of the initially described type which provides switching of two electrically separate switching circuits that are completely independent from one another without significantly increasing construction costs.
This and other objectives are achieved in the present invention by providing an electrical switchgear of the initially described type with electrically separate snap switches having rockers moved by the displacement of the working piston. The rockers move in the housing in parallel moving paths, the paths being arranged to at least one side of the longitudinal center of the working piston.
In the present invention, a complete electrical separation is obtained between the snap switches, and the required additional expenditures are kept low. In particular, these additional expenditures are significantly less than the conventional solutions in which for the switching of two electrically separate switching circuits two electrical switchgears were used with one snap switch respectively.
In order to meet the requirements of an installation space that is as small as possible, it is provided in a preferred embodiment switching rockers which are constructed asymmetrically and have support surfaces assigned to the working piston. The support surfaces are arranged more closely to the longitudinal center line of the working piston than the receiving means with which they are disposed on the holding plate. The result is that an unnecessarily large working piston is not required to actuate the two switching rockers.
In a further feature of a preferred embodiment of the invention, the snap switches are arranged rotated with respect to one another by 180.degree. such that the switching rockers will move in opposite directions. Snap switches arranged this way require very little installation space. A further feature of a preferred embodiment are switches that are constructed of identically designed elements. The switching rockers, despite their asymmetrical shape, are able to have identical construction because of the rotated arrangement of the snap switches.
In a preferred embodiment, the two snap switches switch in the same position of the working piston, in other words, at the same switching temperature. However, it is contemplated to have the switching operations carried out at different temperatures. For this purpose, in a further preferred embodiment of the invention the switching tongues and/or the switching rockers and/or the coupling points for the switching springs of the two snap switches are different from one another and/or are arranged to deviate from one another. In order not to give up the advantage of having the same structural elements, it is sufficient if the individual elements are only slightly plastically bent or arranged at different heights with respect to the working piston in order to obtain the desired different switching times or switching temperatures.
Further objects, features, and advantages of the present invention will become more apparent from the following description when taken with the accompanying drawings which show, for purposes of illustration only, an embodiment in accordance with the present invention.